1. Field of the Invention
The present invention relates to a golf ball and a process for preparing the same, more particularly to the golf ball having a paint film and the process for preparing the same.
2. Description of the Related Art
A conventional golf ball has a paint film on the surface of the golf ball body. The paint film is formed to prevent the deterioration of the golf ball body due to the exposure of the sun light and the weather, as well as impart a gloss to the golf ball body, thereby improving the appearance thereof. It is required for the paint film to have a durable adhesion against the impact, since the golf ball is repeatedly used and hit. Especially, since hitting the golf ball deforms the golf ball body, the paint film is likely to peel off in the case that the paint film covering the golf ball body does not follow the deformation of the golf ball body. In addition, the paint film may peel off when the golf ball is subject to the friction against the golf clubs when hitting the golf ball, and against the ground surfaces such as sand of bunker and rough when landing on the ground.
In recent years, it has been expected to reduce the usage of the solvent-borne paint in view of the environmental problems, and an aqueous paint has been studied to replace the solvent-borne paint used for the golf ball. For example, Japanese patent publication No. H08-71177 A discloses a golf ball where an aqueous polyurethane dispersion having a carboxyl group crosslinked with carbodiimide compound is painted. Japanese utility publication No. H02-11095 B discloses a golf ball where a high molecular weight of an aqueous polyurethane dispersion is coated.
However, carbodiimide compound disclosed in Japanese patent publication No. H08-71177 A is diluted with a solvent, and it is impossible to reduce an amount of the solvent used in the paint, as long as the above carbodiimide compound is used. Japanese utility publication No. H02-11095B discloses ethylene imine as a crosslinking agent for the high molecular weight of the polyurethane, but the usage of ethylene imine is not preferred from the view point of safety and health, since ethylene imine is mutagen. Further, a golf ball having a paint film made from the aqueous paint tends to be inferior to a golf ball having a paint film made from the solvent-borne paint in terms of the durable adhesion.